1. Field of the Invention
The present invention relates generally to the field of semiconductor manufacture and, more particularly, to a semiconductor device, e.g., a random access memory, incorporating an electrical contact to a conductive layer, e.g., a cell plate of a capacitive storage cell, formed in the interior of the semiconductor device.
2. Description of the Related Art
A dynamic random access memory (DRAM) chip is an example of a semiconductor device where reliable electrical contacts to an internal conductive layer must be provided. A DRAM chip typically includes several arrays of memory cells organized to store binary information through storage of different levels of voltage in a capacitive charge storage region of the DRAM chip. A transistor structure, including a plurality of transistors is provided in the DRAM chip to provide access to the charge stored in each charge storage region. Each transistor functions as an on-off switch to open the communication lines between the charge storage region and a microprocessor in communication with the DRAM chip.
A network of electrically conductive cell plate contacts is provided within the structure of the DRAM chip to enable storage of selected voltage levels in each charge storage region. Reliable storage is directly dependent upon the integrity of the cell plate contact. Cell or top plate contacts should exhibit low contact resistance. Accordingly, there is a continuing need for semiconductor devices incorporating reliable electrical contacts to internal conductive layers.
The present invention discloses a novel structure for making electrical contact to a conductive film in a semiconductor structure and a method for making the structure.
In accordance with one aspect of the invention, a contact structure is configured to make electrical contact to a conductive film of an integrated circuit. The structure includes a contact formed from a contiguous volume of conductive material, having a contact leg and an anchor leg. In the illustrated embodiment, the contact leg is formed in a container or depression lined with the conductive film, while the anchor leg extends downwardly generally parallel to the contact leg, beyond the edge of the conductive film. A waist section extends over the edge of the conductive film, joining the contact leg to the anchor leg.
In accordance with another aspect of the present invention, a method is provided for fabricating an electrical contact in an integrated circuit. The method includes providing an insulating layer and forming a conductive container in the insulating layer. A depression is formed in the insulating layer proximate the container. A contact is then formed by depositing a conductive material within a portion of the container and into the depression, making electrical contact to the conductive container.